Pressure relief means for pump



Sept. 1., 1964 R E, HENRY 3,146,720

PRESSURE RELIEF MEANS FOR PUMP Filed Deo. 6, 1961 .'55 54' fg 23a/21,57%7 5.a

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, @WMM United States Patent O 3,146,720 PRESSURE RELIEF MEANS FOR PUlWPRalph E. Henry, Rixford, Pa., assigner to Dresser Industries, Inc.,Dallas, Tex., a corporation of Delaware Filed Dec. 6, 1961, Ser. No.157,438 4 Claims. (Cl. 1031-42) This invention relates to pressurerelief means for a pump, and more particularly to pressure relief valvemeans `for a hydraulic pump of the positive displacement type.

With a hydraulic pump of the positive displacement type such as a gearpump, the pressure in the outlet of the pump varies or pulses inresponse to the quantities or surges of the fluid positively displacedby the pump. These variations or pulsations in the pump outlet and theoutlet line connected thereto cause the normal type of relief valve tochatter or oscillate rapidly and this chattering not only producesundesirable noise but also disturbs the pressure of the fluid throughoutthe hydraulic system connected to the pump outlet, setting up vibrationsthat may even break pipes.

The main object of the present invention is to provide in a pumppressure relief means which do not chatter and dampen or lter outvibrations.

Another object of the invention is to provide such pressure relief meanswhich are adjustable so that the pressure level at which the reliefmeans operates can be varied selectively.

Other objects of the invention are to provide such pressure relief meanswhich are simple in construction, relatively inexpensive to incorporatein a pump, and not likely to get out of order or require repair.

Still other objects and advantages of the invention will be apparentfrom the following detailed description of a preferred embodimentthereof which is illustrated in the accompanying drawings wherein:

FIG. 1 is a vertical central section through a gear pump equipped withpressure relief valve means constructed in accordance with theprinciples of the present invention, and showing the valve in a closedor seated position.

FIG. 2 is an enlarged sectional view of the pressure relief valve meansshown in FG. l but illustrating the Valve in an open or unseatedposition, and further showing only a fragmentary part of the pump body.

The numeral 15 represents generally the body of a gear pump suitablyformed with a lower curved wall 3 and an upper inner curved wall 9 toprovide chambers for a pair of cooperatingrgears 13 and 14, and alsoformed to provide an inlet 11 and an outlet 12. Suitable means (notshown) cause rotation of one of the gears 13 and 14 which in cooperationwith the walls 8 and 9 operate to displace positively fluid from theinlet 11 to the outlet 12.

In accordance with the present invention, means are provided to relievepressure in the outlet 12 should it rise above a predetermined level.For this purpose, an outer wall 15 is spaced from the upper inner curvedwall 9 of the pump body to provide a passage 16 which at one endcommunicates with the outlet 12 and at its other end communicates with acylindrical hole 18 of reduced diameter. The other end of this hole 18is shown as communicating via the passage 19 with the inlet 11. Thepassage 19 is formed preferablyV as shown by an outer wall Ztl and avalve housing portion 17 intermediate the walls 15 and 20. These walls15 and 2t) and portion 17 are preferably formed integrally with the pumpbody 10. The passages 16, 1d and 19 jointly provide a by-` passconnecting the pump inlet and outlet.

The pump body on the downstream side of the hole 1S is formed with acylindrical counterbore as indicated AlCe at 21 to provide an annularseat 22 which faces toward the pump inlet 11.

Movable valve means are operatively associated with the seat 22. Suchvalve means are shown as including a cylindrical sleeve member 23slidably arranged within a bore 24 provided in the pump body portion 17so that one end of this sleeve opposes the seat 22. Preferably the innerand outer corners of the sleeve member 23 v at this end are bevelled orchamfered to provide a relatively narrow annular end face 25 whichisadapted to engage abuttingly the opposing annular seat 22.

Intermediate its ends, the sleeve member 23 is shown as provided with aninternal Wall 26 which extends transversely of the member. This wall isshown as having a central through hole 2S provided with an annulargroove to receive an 0ring 29. The O-ring 29 sealingly embraces acylindrical stem 3). One end of the stem 31B `carries a piston 31 whichis relatively slidingly arranged within the sleeve member 23 and islocated between the transverse wall 26 and the seat 22. The spacebetween the piston 31 and transverse wall 26 provides a chamber 32. Thepiston 31 is shown as having a restricted opening 33 extendingtherethrough which establishes communication between the chamber 32 andthe bypass channel constituted by the passage portions 16, 18 and 19.

Any suitable means may be provided for securing the piston 31 to thestem. As shown, the piston is removably connected to the stem and forthis purpose the stem is shown as having a coaxially projecting neck 34of reduced diameter so as to provide a forwardly facing annular shoulder35 against which the inner face 36 of the piston 31 bears adjacent acentral hole 33 provided in the piston. The outer end of the reducedneck 34 is externally threaded to receive a nut 39 which bears againstthe outer end face 4G of the piston 31. Tightening the nut 39 clamps thepiston 31 against the shoulder 35.

The other end of the stem 3l) is shown as secured to a generallycup-shaped plug 41 having an annular wall portion 42 provided withexternal threads 113 adapted to be screwed into an internally threadedhole 44 provided in the pump body. The hole 44 is coaxial andcornmunicates with the bore 24 for the slide valve member 23. Theadjusted position of the plug 41 relative to the pump body may bemaintained by a lock nut 4S which is threaded on the threads 43 andbears against an outer end face 37 of the pump body portion 1.7. Theouter end portion of the plug 41 is shown as being enlarged and providedwith an out-of-round perimetrical configuration to permit theapplication of a wrench or the like (not shown) to enable the plug to berotated.

The adjacent end of the stem 34B is shown as having a reduced neck 46,leaving an outwardly facing shoulder 47 which engages the inner face 57of the end wall of the plug 41. The outer end portion of the neck 46 isexternally threaded as indicated at 48. The neck 46 extends through acounterbored hole i9 provided in the end wall of the plug 41. Thiscounterbored hole provides an outwardly facing shoulder 5t) againstwhich the inner end face of a nut 51 screwed onto the threaded portion43 bears. T ightening the nut 51 clamps the stem shoulder 47 against theplug face 57.

A helical compression spring 52 is shown as operatively interposedbetween the plug 41 and sleeve member 23 so as to urge the latter towardthe seat 22. Specifically, one end of the spring 52 bears against oneside of the transverse wall 25 and the other end of this spring bearsagainst the inner face 57 of the plug 41.

It will be seen that the preload on the spring 52 can be varied byadjusting lthe axial position of the plug 41 relative to the pump bodyportion 17. Thus by screwing the E5 plug 41 into the body the preload onthe spring 52 is increased, whereas backing off or unscrewing the plug41 partway reduces the preload on the spring. Before making anyadjustment of the plug 41, the lock nut 45 is suitably loosened and thenfollowing this adjustment the lock nut is retightened.

The adjustable plug 41 and lock nut 45 are shown as covered by aremovable cap S3 having attaching iianges 54 opposing the body end face37. A gasket S5 is shown as interposed between the flanges 54 and thisface 37. Removable machine screws 56 pass through holes in the attachingiianges 54 and are received in threaded recesses provided in the pumpbody.

The space between the sleeve member 23 and plug 41 which may vary involume due to movement of the sleeve member relative to the stationaryplug, is connected to the passage portion 19 by the lateral branchpassage 58 formed in the body portion 17 and which intercepts the bore24 and hole 44.

From the foregoing, it will be seen that the piston 31 acts as a iixedwall element spaced from the seat 22, the face 40 of which is constantlyexposed to the pressure in the pump outlet 12. Also, the sleeve member23 acts as a closure member cooperable with the seat 22 and movable withrespect to the iixed piston or wall element 31. Another way of viewingthese elements is to regard the sleeve member 23 with its transversewall 26 as a movable cylinder member in which the piston 31 is fixedalthough slidable relative to the annular wall.

In operation, it will be seen that the pressure in the pump outlet 12 istransmittable to the chamber 32 formed by the opposing and spaced walls31 and 26 through the restricted opening 33 arranged in the wall memberor piston 31 and via the connected passage portions 16 and 1S. If thepressure within the chamber 32 is high enough to develop a forcedirected from left to right as viewed in the figures to overcome theoppositely directed force exerted by the spring 52, this spring willyield and allow the sleeve member 23 to move away from its seat 22,thereby establishing communication between the passage portions 18 and19 and hence between the pump inlet and outlet. When the force exertedby the fluid pressure within the chamber 32 is inadequate to overcomethat exerted by the spring 52, this spring will maintain the sleevemember 23 against the seat 22, as illustrated in FIG. 1.

The purpose of the restricted opening 33 in the wall element or piston31 is to dampen or filter out the vibrations or pressure fluctuations inthe pump outlet 12, while allowing `the more or less steady state ormean pressure to be transmitted to the chamber 32. The smaller thetransverse area of the restricted opening 33 in the wall element orpiston 31 relative to the volume of lthe chamber 32, the more dampingeffect produced.

Another purpose of the restricted opening 33 in piston 31 is to act as ametering orifice in restricting the velocity of movement of sleeve 23.In order for sleeve 23 to move, fluid must be displaced through therestricted opening 33. This prevents overcontrolling and consequentpressure surges.

As noted hereinabove, the preloading of the spring 52 is variable byadjusting the plug 41. This adjustment and hence preloading determinesthe pressure within the bypass channel at which the pressure reliefvalve member 23 will open or unseat.

Since variations and modifications of the precise construction of theinvention illustrated may occur to those skilled in the art, the scopeof the invention is to be measured by the appended claims.

What is claimed is:

1. In a pump including a body having a by-pass connecting an inlet andan outlet, the combination therewith of pressure relief means comprisinga seat in said by-pass, a xed piston element spaced from said seat andhaving two opposite sides one of which is constantly exposed to lthepressure in said outlet and also having an opening therethroughconnecting said sides, a movable cylinder member having an annular wallslidably arranged on said element and forming jointly therewith achamber on the other side of said element communicating with saidopening, and yielding means urging said member toward said seat, saidmember when seated blocking said by-pass but when unseated unblockingsaid by-pass.

2. In a pump including a body having a by-pass connecting an inlet andan outlet, the combination therewith of pressure relief means comprisinga seat in said by-pass, movable valve means operatively associated withsaid seat and including a sleeve and a wall arranged transversely of andwithin said sleeve, yielding means urging said sleeve toward said seat,said sleeve when seated blocking said by-pass but when unseatedunblocking said by-pass, and a iixed piston arranged Within said sleevebetween said wall and seat to provide a chamber, said piston having anopening therethrough communicating with said chamber.

3. In a pump including a body having a by-pass connecting an inlet andan outlet, the combination therewith of pressure relief means comprisinga seat in said by-pass, movable valve means operatively associated withsaid seat and including a sleeve and a wall arranged transversely of andwithin said sleeve and having an opening therethrough, yielding meansurging said sleeve toward said seat, said sleeve when seated blockingsaid by-pass but when unseated unblocking said by-pass, a fixed stemextending through said opening and slidably sealed with respect to saidwall, and a piston secured to said stem and arranged Within said sleevebetween said wall and seat to provide a chamber, said piston having anopening therethrough communicating with said chamber.

4. In a pump including a body having a by-pass connecting an inlet andan outlet, the combination therewith of pressure relief means comprisingan annular seat surrounding said passage, valve means slidably arrangedon said body opposite said seat and including a sleeve having an endadapted to engage said seat and also including a wall arrangedtransversely of and within said sleeve intermediate the ends thereofsaid wall having a central opening extending therethrough, a stemslidably extending through said opening, a piston secured to one end ofsaid stem and arranged within said sleeve between said wall and seat toprovide a chamber, said piston having an opening therethroughcommunicating with said chamber, a member adjustably mounted on saidbody and secured to the other end of said stem, and spring meansoperatively interposed between said wall and member and having a preloadvariable by adjustment of said member.

References Cited in the file of this patent UNITED STATES PATENTSRe.24,892 Banker Oct. 25, 1960 168,807 Taylor Oct. 11, 1875 677,470Richter July 2, 1901 1,285,819 Smith Nov. 26, 1918 2,013,260 Waterous etal Sept. 3 1935 2,305,518 Dunmire Dec. 15, 1942 2,437,791 Roth et al.Mar. 16, 1948 2,456,651 Schmiel Dec. 21, 1948 2,684,631 Anthony et al.July 27, 1954 2,996,013 Thompson et al. Aug. 15, 1961

2. IN A PUMP INCLUDING A BODY HAVING A BY-PASS CONNECTING AN INLET ANDAN OUTLET, THE COMBINATION THEREWITH OF PRESSURE RELIEF MEANS COMPRISINGA SEAT IN SAID BY-PASS MOVABLE VALVE MEANS OPERATIVELY ASSOCIATED WITHSAID SEAT AND INCLUDING A SLEEVE AND A WALL ARRANGED TRANSVERSELY OF ANDWITHIN SAID SLEEVE, YIELDING MEANS URGING SAID SLEEVE TOWARD SAID SEAT,SAID SLEEVE WHEN SEATED BLOCKING SAID BY-PASS BUT WHEN UNSEATEDUNBLOCKING SAID BY-PASS, AND A FIXED PISTON ARRANGED WITHIN SAID SLEEVEBETWEEN SAID WALL AND SEAT TO PROVIDE A CHAMBER, SAID PISTON HAVING ANOPENING THERETHROUGH COMMUNICATING WITH SAID CHAMBER.